The passage of time has mostly numbed me to the disappointment, but I used to have similar feelings on the ending. I get where you're coming from.
In a vacuum, I actually don't really have a problem with the endings. They would have worked if it was a single game and not a series. In fact I quite like the
ending, I find it fitting.
The thing is, viewed in the context of "your choices matter", the consequences of your decisions over three games and ~5 years finally coming to bear on the game world, it was basically a total failure. You could have jumped into the series at ME3 and little would have changed. That's not what they promised and not what fans wanted.
Realistically we should have expected as much. It's a pretty ambitious goal and one difficult to achieve for a series with the production value of Mass Effect. Given more time, and/or less focus on other areas of the game, they could've done it. But with a ~2.5 year average turnaround, a goodly amount of content, and AAA-title graphics, it's a somewhat lofty objective.
I would have been OK with an average implementation of this idea. Say, 10 endings instead of 3, and the last 1-2 hours of the game being different depending on the choices you've made. Pretty achievable if you ask me.
They didn't even come close.
The "Extended Cut" DLC was a cheap PR move to counter the backlash throughout the gaming community (although there were plenty of apologists in the press...). It sucked.
It's funny that 4 years later I still get worked up enough to write a post of this length. I guess it's a testament to how much I enjoyed the first two games and the level of goodwill I had for the developers. They certainly lost it.
If any of you feel at all similarly, don't buy Andromeda new. Get it used, or play a friend's copy if you're on PC. Vote with your wallet y'all.